I am new to simulations and have two designs I am trying to test. Each is for the internal connection of plastic tubing (images attached). I am trying to set up simulations that will test the tensile strength of each. I also want to know if the plastic tube or threads/split ring will fail first.

The first option screws in, theoretically cutting threads. The second has a split ring that would expand and bite into the plastic as the body is pulled out. I have been trying to use a displacement study but am either not setting it up correctly or using it incorrectly. 

Any help or links to videos would be greatly appreciated. Thanks